Method of and apparatus for separating materials of different specific gravities



1.900.190 NG MATERIALS TIES March F533- w. c. MENZIES METHOD OF AND APPARATUS FOR 5E ATI OF DIFFERENT SPECIFIC AVI Filed Aug. 22, 1931 4 Sheets -Sheet 1 gwovnkoo WZZ-L/AM C. ME VZIES,

March 7,- 1933. w c, MENZIES 4 F AND APPARATUS FOR SE METHOD 0 PARATING MATERIALS OF DIFFERENT SPECIFIC GRAVITIES Filed Aug. 22, 1931 4 Sheets-Sheet 2 m mm U Qwowntoz MUNI March 7, w. c. MENZIES APPARATUS FOR SEPARA METHOD OF AND TING MATERIALS OF DIFFERENT SPECIFIC GRAVITIES Filed Aug. 22, 193].

4 Sheets-Sheet s W. C. MENZIES ME'I'HQD OF AND APPARATUS FOR SEPARATING M March 7, 1933.,

ATERIALS OF DIFFERENT SPECIFIC GRAVITIES Filed Aug. 22, 1931 4 Sheets-Sheet 4 R w m vm mm H W Muzzle BY div-4 ATTORNEYS Patented Mar. 7, 1933 UNITED STATES PATENT OFFICE WILLIAM C. MENZIES, OF SCRANTON, PENNSYLVANIA manner) or ANDAPPABATUS roa SEPARATING m'rnams or DIFFERENT SPECIFIC GBAV'ITIES Application filed August 22, 1931. Serial No. 558,812.

chanical agitationeflecting classification and separation of the materials.

With prior art methods and apparatus of the general type to which my invention pertains, the separation of materials of substantially difierent specific gravities has offered little diflicult But where material of intermediate speci c gravity is also present v in the mixture, and especially where it is of a specific gravity closely approaching that of the material of value to be separated from the other materials as impurities, the separation is attended with difliculty. This is due to the tendenc of the material of the intermediate specic gravity to go with the material of value, or, when particular steps or means are employed to separate out the material of the intermediate specific gravity with the other materials of the reject, to the tendency of the material of value to be also carried along so that much of it is lost in the reject.

The foregoing difliculties are well illustrated in the case of the separation of coal from its impurities which generally are a very poor grade of coal called boney, and rock, pyrites, slate and the like, commonly designated simply as slate. The material of value, the high grade coal, is of the lowest specific gravity, the slate materials are of the highest specific gravity, and the bony is the material of the intermediate specific gravity.

In methods and apparatus employing an upflowing current of water for the Stratification of the materials according to their different specific gravities, generally the good coal which is to be separated out as the material of value is floated off into a discharge at the top of the liquid column, and the materials of intermediate and higher specific gravities are separated out at the bottom. But with all such methods and apparatus of the prior art, so far as I am aware, the separation is not sufficiently well defined to give the greatest possible recovery of the high grade coal. Either the lighter impurities, such as the bony, are carried over into the discharge with the high grade coal 'or much of the high grade coal is carried along with the settling and discharge of the bony or other'impurities and wasted in the reject. I 0

One reason why these defects arelnot overcome or avoided in these prior art methods and apparatus is the substantially unvaried condition of the fluid medium in which settlin Stratification of the materials'occur accor ing" to their ditfe rent specific gravities. For example, with methods and apparatus employing an upwardly flowing current of water forthe floating 0E and discharge of the high grade coal at the top and the settling ofthe heavier materials through the column of liquid, the'lighter refuse material tends to so accumulate immediately beneath the stratum of coal at the top as to be forced over to some substantial extent with the coal into the discharge.

This particular defect can be avoided by substantially reducing the velocity of the upward "flow of the water so as to give but slightly hindered or practically free settling of these impurities. But upon such reduction there is a tendency for all the materials to settle through the column of liquid at so comreject ends of the apparatus to maintain the proper balance eliminating both of the referz'ed-to defects.

Other methods and apparatus of the prior art employ a suspension in the water column of finely divided solid particles, such as sand .for example, of specific gravity greater than that of the high grade coal and most of the impurities to be separated therefrom, with the mixture mechanically or hydraulically agitated to maintain the suspension. In this denser fluid medium employed. for the Stratification and separation out of the materials, the material of value, for example the high grade coal, floats atthe top and the heavier impurities settle through the fluid mass at varying rates according to their varying specific gravities. Some appreciable hydraulic head and current flow is, of course, still employed to discharge the value coal at the top of the column. There is therefore still some tendency to the discharge with the value coal of/some of the accumulated lighter impurities near the top of the column, and the discharge of some of the value coal with the reject if the hydraulic conditions are changed sufliciently to entirely eliminate the first-mentioned defect; for example, by reducing the upward flow of the water or the agitation of the fluid mass upon observation of the materials discharged at the reject end of the apparatus. I

Accordingly, a primary object of my invention is to provide a method and apparatus of the general type of these prior art methods and apparatus but which will be free from their defects referred to above.

In other words, the general object of my invention is to provide a method and apparatus by which coal or other minerals may be separated from their mixtures substantially free from. the impurities usually found mixed therewith. V

As in the prior art methods and apparatus briefly referred to above, my invention employs a body or column of liquid, such as water, for the classification by settling of the materials of the mixture fed thereto. Preferably nothing is added to the liquid except the materials of the mixture fed thereto so that the fluid mass preferably consists only of the body of liquid and those materials.

As in the prior art methods and apparatus, so also with the method and apparatus of my invention, the hydraulic state ofthe liquid column or of the entire fluid mass (that is, its state or condition of motion) has an efl'ect on the settling of the materials therein.

To attain its object referred to above, my invention contemplates changes in the hydraulicstate of the fluid medium eflecting the settling, in accordance with changes of its density due to stratification of materials therein and settling out of materials therefrom, so decreasing the resistance to downward settling when the density increases as to prevent material of the intermediate specific gravity from accumulating so near the top of the column as to go over into the discharge with the material of the lowest specific gravity, and so increasing the resistance to downward settling when the density is decreased as to prevent the settling of the material of the lowest specifie gravity with the other materials to a common discharge.

While not necessarily limited thereto, my

invention preferably employs a variation in the liquid upflow in the classification or sorting column as the factor producing the changes referred to in the hydraulic state of the fluid medium effecting the classification and settling, a lessening of the velocity of upflow being employed to decrease the resistance offered by the fluid body to downwardsettling of the materials and an increase of the velocity of upflow being employed to increase that resistance.

Preferably also the changes in the liquid upflow contemplated by my invention are such as to produce an intermittent substantially free and hindered settling of the materials fed to the sorting column. For the hindered settling, the upward flow of the liquid is at a predetermined maximum velocity designed to float the material of the lowest specific gravity off into the discharge at the top of the column while permitting the ready downward settling therefrom of the materials of substantially higher specific gravity. Under this hindered settling, material of an intermediate specific gravity fairly closely approaching that of the lightest material tends to stratify out near the top of the column until the density of this stratum becomes such that, if the hindered settling were continued, more or less of this material would be forced by the current upflow over with the lightest material into the discharge at the top. of the column. To avoid this, the substantially free settling, by reduction in the upward current flow, is brought about through the increased density of the fluid mass as a controlling factor. The substantiallyfree settling, of course, rapidly reduces the density of the fluid mass, and if it were continued the lightest material would be carried down with the heavier to a common discharge. To avoid this, the hindered settling, by restoration of the original upward current flow, is brought about through the decreased density of the fluid mass as the controlling factor.

To make the density of the fluid mass the controlling factor in the changes just referred to, my invention preferably employs means responsive to variations in resistance to the upward flow of the liquid offered by the material itself as it varies in density in the classification or sorting column. One convenient form such means may take comprises bring about a less hindered or substantially free settling condition. Likewise, as the density of the fluid mass in the sorting column decreases andthereby less resistance is offered to the upflow of the water, the water backed up in the water-expansion chamber returns to the sorting column and the lowering water in the chamber is utilized to operate the valve means for restoration of the original upflow current in the sorting column giving the hindered settling.

, The foregoing and other objects and advantages of my invention and its operating principles both as to the method and appara-' paratus shown in Fig. 7 but at a right angle thereto. a

The illustrated apparatus is of a form esm pecially adapted forthe separation of coal from its impurities, though it may be, used also for the separation of other minerals. Since the method and apparatus of my invention as applied to the separation of coal from its impurities involves substantially the same principles as when applied to the separation of other minerals, the present description will be confined to the separation of coal as a typical instance of use serving to present the essential principles of the invention.

The particular form of apparatus embodying my invention which is shown in the drawings includes a main receptacle or tank so supplied with water as to function as a classification or sorting body or column for the coal mixture fedthereto. In the form as shown, this,tank-has a cylindrical upper portion 1, an intermediate portion 2 of an in- ,tus and the structural principles 'of the in- 29 vention as to the apparatus will more fully appear from the following concrete examples.

It is to be understood, however, that while these examples present one mode of practicing the method and one form of apparatus of my invention found particularly desirable,

theinvention is not limited thereto, and that it includes other modes of practicing the method and other forms and constructions of the apparatus within the scope of the. ap- 39 pended claims.

In the drawings, which are somewhat diagrammatical:

Fig. 1 is a top plan view of one form-of the apparatus of my invention;

Fig. 2 is in part aside elevation and in part aver-tical sectional view of that apparatus along the line 2-2 of Fig. 1, and showing the m'aterials'therein under the condition of maximum hindered settling;

Fig. 3 is a cross sectional view, on an enlarged scale, along the line 3-3 of Fig. 2, and showing a perforated plate employed in the lower portion of the sorting column or tank of the apparatus;

Fig. 4 is a view jof the apparatus identical with Fig. 2, but showing the materials therein under the condition giving a freer settling than represented in Fig. 2;

Fig. 5 is a vertical side-elevational view,

- 53 on a larger scaletha'n that of Figs. 2 and 4,

of the upper portion of the float-chamber of the apparatus, with an adjustable bracket on the upper end of that chamber forming a part of'mechanism for adjustably control- 53 ling the upflowof water in the sorting column;

Fig. 6 is a view of the same parts of theapparatus shown in Fig. 5, but at a right angle thereto;

Fig. 7 is a side-elevational view, on a larger scale than that of. Figs. 2 and 4, of the disc of the valve controlling the upflow of water in the sorting column, and of an adjustable connection between the valve disc and the solenoid employed to operate the valve; and

verted cone shape with its walls converging downwardly to a tubular lower portion .3 of a substantially lesser diameter than that of the uppermost portion. This lower tubular portion or member 3 of the classification or sorting tank communicates with and rises from a chamber 4 through which the water for the sorting column is supplied in the manner hereinafter more fully set forth.

The chamber 4, together with an extension 5 extending obliquely upward to an open end, also forms a combined water-expansion chamber and conveyor boot, one function of which is 'to receive from the sorting column the refuse materials settling downward therethrough and to convey them away from the apparatus.

As. the conveyor, indicated by the numeral 6, is the usual flight conveyor of well known construction, it is sufficient to here state that its receiving end is journaled in the bottom portion of the chamber 4 in the line of dischar e of the refuse material through the tubu ar portion 3 of the sorting tank, and

fits deliveryend extends beyond the upper open, end of the boot in which it is located. It is operated by a head shaft 7 adjustably mounted in the brackets 8, which shaft may be driven by any suitable means.

Means are preferably employed for agitating the fluid mass in the sorting tank. For that purpose, in the illustrated apparatus, that tank is provided with mechanical agitating means comprising a series of'rotating;

blades 9 driven by shaft 10 upon which they are mounted, the shaft 10 being suitably mounted as shown to extend axially within the tank and thereabove so as to be rotated by the gears 11 and 12 which in turn may be driven by any suitable means.

The coal mixture which makes up the feed to the apparatus in its illustrated'use is dematerial is delivered to a vibratory screen 17 through which the water is drained as the.

material travels thereover to a final line of discharge from. the apparatus indicated at 19. Any suitable means may be employed for imparting vibratory movement to the screen. As shown somewhat diagrammatically, the screenl? is suspended by spring boards 20 from the cross piece 21 of the apparatus frame and is oscillated or vibrated by a board and eccentric 22 operated from the shaft 23.

One of the desirable features of the apparatus is the provision of a constant static head for the supply of water to the sorting or classification tank to form the liquid column therein. In the illustrated apparatus, this takes the form of an overhead receptacle or static head tank 24 supplied by a fresh water pipe 25 having a Valve 26 automatically controlled in the well known manner by a float 27 in the tank 24, as more or less diagrammatically indicated on the drawings. /Vater is supplied under pressure from this tank 24 through pining 28 and valve therein to the water expansion chamber 4, the valve being indicated in Figs. 2 and 4: by the disc 29 on'its stem.

To conserve the water drained from the material advancing over the screen 17, a drainage receptacle 30 is mounted on the frame of the apparatus immediately beneath the screen, and from this receptacle the water is returned by the pump 31 through the pipe 32 to the overhead tank 24.

Any suitable source of power and powertransmission means may be employed to drive the flight elevator 6, the shaft 10 of the agitator, the screen 17 in its vibratory movement and the pump 31. As shown diagrammatically, an electric motor 33 is employed to' drive these parts through belt and chain drives 345as required. I

An even distribution of the uprising current of water entering the main tank for the settling and'classification operations is desirable; and as a means therefor the plate 35 with numerous uniformly distributed openings 36 therethrough, as shown on an enlarged scale in Fig. 3, is provided within the tubular lower portion 3 of the sorting tank.

With the valve 29 rotated to its maximum open position, the water supplied through pipe ZS-under its constant static head to the wearer)? receiving side of this valve is admitted therethrou-gh to the chamber 4 of the apparatus in maximum volume to produce a maximum velocity flow of the water from the chamber 4 upwardly into the tubular member,3 of the sorting tank, through the openings 36 of the" plate 35 therein, and therefrom upwardly through the remainder of the tank to overflow into the launder at the top thereof. This maximum velocity flow of water through the perforated plate produces a hindered settling classification of the materials fedto the tank. The plate 3.5 with the numerous open ings 36 uniformly distributed over its area functions to maintain an even distribution of the uprising currents which produce the hindered settling as the plate presents sufiicient resistance to the upward flow of the water through the tubular member 3 to maintain auniform distributionof the water entering the sorting tank regardless of the inequalities in the distribution of materials through the fluid mass above the plate or inequalities in the water pressure or velocity on the under side of the plate due to frictional resistance of the water on the lower wall of the tubular member of the tank.

The coal mixture having been delivered to the center of the tank, mixes with the agitated Water to form a fluid mass, at first thin but gradually thickening asthe mass forms into astratified mobile body under the hindered settling. The heavy material, such as slate,

settles fairly rapidly entirely through the fluid mass and. into the chamber 4 Where it is received by the conveyor 6 and carried away as refuse. The purer or better grades of coal within the fluid mass, asthe material of lowest specific gravity, assume under the hindered settling an uppermost position, and as it accumulates it is carried over by the up- Wardly flowing water into the launder 15 as value material. I Other materials of intermediate specific gravity, such as the bony or like impurities which are to be rejected as refuse, stratify out beneath the layer of good coal instead of dropping through with the slate. As this material accumulates, if the maximum velocity of the upward current of water were maintained, more or less of it would be forced over by the upfiowing current with the good coal into the discharge with the value material at the top of the column.

To avoid the foregoing defect, as hereinbefore stated, my invention contemplates means to automatically reduce-the velocity of the upfiow of water in the sorting col- .umn as the density of the material accumulating therein increases, that reduction of course reducing the resistance to settling and thereby enabling the accumulated bony or like refuse material to settle downwardly of water in the sorting tank so as to produce the variably hindered settling or the intermittent hindered and substantially free settling, includes an electric solenoid 37. solenoid has its, core connected through a rod 38 to the disc 29 on the stem of the rotatable valve which controls the flow of Water to the sorting tank so as to partially rotate or oscillate that valve in the opening and closing the desired maximum and minimum upward current flow of water in the sorting tank. 1

Desirably, means may be employed for an adjustable setting of the valve in respect to its maximum and mmimum open positions when operated by the solenoid. 7 One form such means may take is shown in Figs. 7 and 8. As there shown, the disc 29 is provided with two circular series of holes 29' and 29 at different distances from the valve stem or bolt passing through the axis of rotation of the disc, and one end of the rod 38 may be removably secured to the disc in the location of any one of these holes by the bolt-and-nut attachment 38, with the selected hole in the valve disc and through the apertured head of the rod, as shown more particularly in Fig. 8. The other end or foot of the rod 38 is pivoted to the core of the solenoid and the rod is formed as a divided or two-part rod with a turnbuckle 38" intermediate its ends for adjustment of the length of the rod and consequently of the length of the connection between the valve disc and the core of the solenoid to accommodate theinitial angular setting of the valve for the desired maximum and minimum open positions of the valve upon the upward and downward stroke, of

the core of the solenoid.-

Fig. 2 indicates the opened position of the water-control valve 29 to the extent determined upon for the maximum velocity of upward flow of water in the sorting tank and Fig. 4 indicates the extent of movement toward closed position for the minimum velocity.

The electric solenoid is actuated by float 39 riding on the surface of the water in cham-- her-'40 which chamber is in open communication at its lower end with the extension 5 of the water chamber 4, so that the chamber 40 is a part of the water-expansion chamber. As shown more or less diagrammatically in Figs. 2 and 4, the upper andlower terminals 41 and 42 of the solenoid circuit and the brid e bar 43 on the stem of the float function as a switch for directing the current through the solenoid in opposite directions for its two-way operation in oscillating the This es sufliciently in the float chamber for the float to elevate the bridge bar 43 into contact with the upper terminals 41, the solenoid is energized to oscillate the water-control valve 29 to the partially closed position shown inFig. 4; and when the water falls sufficiently in the float chamber for the float to lower the bridge bar into contact with the lower terminals 42, the solenoid is energized to oscillate the valve 29. from its position shown in Fig. 4 to its more open position shown in Fig. 2.

Other means for the automatic operation of the water-control valve 29 may be employed such, for example, as a large float connected to the valve stem through a system of mechanical levers or the use of hydraulic or pneumatic systems to actuate the valve to any desired extent when the float is raised or lowered by the changing water level in the float chamber.

The apparatus is shown in Figs. 2 and 4 as used in the performance of the method of my invention. Fig. 2 illustrates the condition of the fluid mass in the classification or sorting tank when there has accumulated therein, under the maximum velocity of water upfiow and consequently hindered settling, a large percentage of relatively light refuse, the top of which is coming relatively close to but is yet within a safe distance from the overflow point of the desired uality of clean coal. It is to be noted that ig. 2 represents the water-control valve 29 open to its maximum position as determined by the operation of the solenoid and the initial setting of the valve on the connections between it and the solenoid whereby a maximum velocity of the upward current of water through the lower tubular portion 3 of the sorting tank and the perforated plate'35 therein is created.

This maximum velocity of upward flow of water in the sorting tank presents themaximum resistance to the downward fall or 'settling of the particles of refuse and results in only the heavier ones dropping through the perforated plate 35 and on to the receiving end of the conveyor 6 in the chamber 4. With the valve in this maximum open position as shown in Fig. 2, therefore, cumulates a large percentage of particles having an'intermediate specific gravity between that of the pure coal and the heavy refuse until this stratum of material becomes so dense as to substantially increase the resistance to the upward flow of water through the mass and'consequently increases the head of water in the water expansion chamber 45 and the communicating float chamber 40.

The foregoing condition is represented in Fig. 2 in which the fluid mass in the sorting tank is represented as relatively much denser and the height of the intermediate-specificthe fluid mass acof the goodcoal than represented in Fig. 4

which is intended to show the conditions under the less hindered or substantially free settling. In each of these views the particles of good coal, as the material of lowest specific gravity, are represented in solid black, while the particles of the refuse are represented in I sponding reduction in the resistance ofl ered by the water to the downward falling or settling of the particles of material undergoing classification. The result is that the material of the intermediate specific gravity as well as the heavier drops through the perforated plate in the bottom portion of the sorting tank into the chamber 4 and upon the receiving end of the refuse conveyor therein, so that the danger of the material of intermediate specific gravity going over with the good coal into the discharge at the top of the column is avoided.

With the valve 29 in this minimum 0 en position as represented in Fig. 4, the uid mass in the settling tank gradually becomes less dense due to the dropping out therefrom of the particles having 'an intermediate specific gravity between that of the pure coal and the heavy refuse. This lessened density as well as lowering of the intermediate specific gravity material substantially below .the level of the discharge for the good coal at the top of the column is shown on Fig. 4 as compared with Fig. 2.

' As the material of the intermediate specific gravity thus drops out of the fluid mass in the sorting column, that mass because of its lessened density offers less resistance to the upward flow of the water in the sorting tank and as a consequence the head of water in the float chamber 40 decreases. The water level in the float chamber therefore gradually lowers, Fig. 4 illustrating the float switch about to make the contact, with the lower terminals 42, which will actuate thesolenoid 37, in the reverse direction to the-original first-mentioned actuation,.to oscillate the water-control valve 29 again to its maximum open position shown in Fig. 2. When this occurs the maximum velocity upward flow of water to the settling chamber is restored to again produce the hindered settling. 1

It is sometimes desirable to adjust the position of the terminals of the float switch.

aeoareo As a convenient arrangement for this, the

bracket 44 in which the upper and lower terminals 41 and 42 of the solenoid circuit are mounted may itself be mounted for lengthwise adjustment on the upper-end por- 'tion of the float chamber 40; for example,

by an ordinary'slot and bolt mounting, so

through the cylindrical wall of the chamber" and the slots in the bracket, nuts on the outer projecting ends of the bolts then removably securing the attachment. Obviously all that is needed for an up or down adjustment of the bracket is the loosening of the nuts and the sliding of the bracket on the bolts to the desired position, and the new adjustment is then secured by tightening the nuts." Also, as shown, the cross supports for the upper and lower contacts 41 and 42 are secured by bolts passing through the .slots in "the bracket and therefore these contacts are also ver- "tically adjustable in the bracket. This adjustability of the terminals with respect to the water level in the float chamber 40 permits a variation in the control of the water valve 29 in respect to the cdntrol factor of density of the fluid mass inthe settling chamber. For example, it may be found that with the terminals set at a certain height the bridge bar 43 of the float stem does not make contact with the upper terminals 41 of the solenoid circuit until the density of the fluid mass in the sorting chamber has reached the point causing the upflow current of water to force some of the lighter refuse over with the good coal into the discharge at the top of the column. To correct this defect, these terminals may be lowered to cause the contact to be madewhen a lesser density of the fluid mass in the sorting column is reached. Likewise, during .the condition of less hindered settling resulting from the reduction in the velocity of the upflow of water in the sorting column, it may be found that the bridge contact bar 43 of the float stem does not make contact with the lower terminals 42 of the solenoid circuit to restore the maxi mum velocity of the upward flow of water and the consequent hindered settling before the density of the fluid mass in the sorting tank has been so decreased that some of the good coal settles downwardly with the refuse to the discharge at the bottom. Then the height of the terminals may be adjusted to cause that contact at a sufliciently higher density of the fluid mass to avoid thedefect.

11 this is of course possible because the float c amber'functions as a balancing column in the maximum and ward settling of the the sense that the height of the water level in the sorting column to the upflow of water, pends upon the density of the fluid mass.

It is thus clear that the illustrated apparatus may be so used that before the good coal gets anywhere near a point in the sorting tank rendering it possible for that coal to get into the reject, the float switch comes into operation to open the water-control valve to an extent restoring the hindered settling and preventing any possible leak of thegood coal into the reject. Also, before the intermediate-specifidgravity material gets near enough to the top of the sorting column to render it possible for that material to be forced over by the upflowing water into the value discharge with the good coal at the top of the column, the float switch again comes into the water-control valve tooperation to move sufficiently to bring ward its closed position about the freer settling which immediately lowers the refuse material away from the coal discharge and thereby absolutely prevenlts impurities from getting into the good coa It is also apparent'that the operating connections between the solenoid core and the stem of the water-control valve 29 permits an angular-adjustment of that valve with respect to the solenoid which operates it, so that the valve may be adjustably set for any desired maximum and minimum open position when operated minimum velocity of upward flow of water in the settling tank may .be adj ustably determined.

With perhaps most coal mixtures, the setting of the water-control valve should be such that when operated by the solenoid in the manner described the maximum and minimum open positions give respectively a hindered and a substantially free settling to avoid forcing the lighter refuse over with the good coal into the discharge at the top of the column. With other mixtures, substantially free settling may not be required but rather a less hindered settling than obtains with the maximum open position ;of the water-control valve, so that the condition required is a variably hinderedsettling.

In the foregoing description, the expression substantially free settling is employed as meaning such a reduction in thevelocity of the upward flow of water in; the sorting or classification tank as to present no substantial resistance by the water to the downmaterials. As already stated, the water-control valve is operated back and forth by the solenoid between adjustably set maximum and minimum open positions, which means, of course, that the upflow of water through the sorting tank is continuous but changes in velocity between which resistance in turn deby the solenoid. Thus v produce a the two extremes of maximum and minimum as determined by the settling of the valve. At the minimum as well as the maximum velocity of the upflowing current there is, as hereinbefore stated, a settling out of the heaviest materials downwardly of the sort ing column to the conveyor, at the maximum velocity the materials of intermediate specific gravity tend to accumulate in strata immediately below the good coal as the material of lowest specific gravity at the top and at the minimum velocity of the upward current this material of the intermediate specific gravity settles downwardly to the discharge at the bottom. Preferably the minimum velocity of the upflowing current through the body of liquid in the sorting column is such as to still sustain the materials of the lowest specific gravity, in this instance the good coal, in the body of the liquid in the sorting column, but to avoid the tendency of some of that material to be physically carried downwardly with the materials of the intermediate specific gravity to the refuse discharge the change is made from minimum back to maximum upward current flow.

Only one water-supply pipe is shown in the drawings, the pipe 28 leading to the cham her 4 at the bottom of the tank but it will be understood that the sorting tank may be provided with one or more valve-controlled water-supply pipes for additional water found desirable in maintaining the proper fluidity of the contents of the tank.

In the use of the method and apparatus for ,the separation of coal from its impurities,

the coal mixture is preferably sized before being subjected to the classification and separation treatment.

What is claimed is:

1. A method of separating materials of at least two different specificgravities from a mixture containing them which comprises feeding said mixture to a column of water, effecting such an hydraulic state of said column by movement of the water therein as to hindered settling of the materials of thesecond lowest specific gravity in said column and a floating of the materials of the lowest specific gravity thereabove to a positionof discharge, and so changing the hydraulic state of said column by reduction of the movement of the water therein as the density of the fluid mass in the column increases as to produce a sufiiciently free settling to prevent the materials of said second lowest specific gravity from being discharged with the materials of the lowest specific gravity 2. A method of separating materials of at least twodiiferent specific gravities from a mixture-containing them which comprises feeding'said mixture to a water-sorting column, effecting such an hydraulic state of said column by uniformly distributed currents I therein as to produce a hindered settling stratifying the material of the next lowest specific gravity near the top of the column and floating the material of the lowest specific gravity thereabove off to a discharge from the column and as the density of said fluid mass increases due to said settling so changing the hydraulic state of said column effecting the settling as to prevent the accumulation of said material of the next lowest specific gravity near enough to the top of the column to cause its discharge with the material of the lowest specific gravity.

3. A method of separating materials of at least two different specific gravities from a mixture containing them which comprises 7 feeding said mixture to a column oftwater,

efi'ecting such an hydraulic state of said column by movement of the water thereinas to produce a hindered settling of the materials of the lowest and next lowest specific gravities stratifying said materials in the order of their specific gravities near the top of said column with the materials of the lowest specific gravity floating upon the stratum of the other material in a manner to discharge material from the upper stratum over the rim of the column and as the density of the bottom stratum increases due to said hindered settling so changing the hydraulic state of said column as to produce a sufliciently free settling to lower said bottom stratum below the point of possible discharge of material therefrom over the rim of the column.

4. A method of separating materials of at least two different specific gravities from a mixture containing them which comprises feeding said mixture to a column of water with which it forms a fluid mass, effecting movement of the water through said fluid mass in a manner to produce a hindered settling'stratifying the materials of the lowest and next lowest specific gravities in the column with the lightest material uppermost in a osition to discharge over'the rim of the co umn and as the density of the bottom stratum increases due to said hindered settling so reducing the movement ofthe water through said mass as to produce 'a sufliciently free settling to drop material from said bottom stratum through the column to a bottom discharge and as the density of said fluid mass is thus decreased restoring the hindered settling so as to thereby prevent a suflicient accumulation under the hindered settling of said material of the next lowest specific grav-' ity to overflow the rim of the column and to prevent under the freer settling the discharge of material of the lowest specific gravity with that of the next lowest specific gravity at thebottom of the column.

5. A method of separating materials of different specific gravities from a mixture containing them which comprises subjecting said mixture with water as a fluid mass in a suitaeoaaae I said mixture to be carried along to anotherpoint of discharge and the material of intermediate weight to be suspended between said points of discharge, and as the density of said fluid mass increases due to accumulation of said last-mentionedmaterial in suspension decreasing the velocity of said current to settle said last-mentioned material to a point of discharge other than the point of discharge for said lightest material. Q

6. A method of separating coal or other mineral of lower specific gravity than the materials mixed therewith comprising sub- ]ecting the mixture in a sorting column to a rising current of water of a velocity causing the coal to overflow the rim of the columnand the heavy material to settle downwardly through the column to a lower discharge and upon accumulation of material of an intermediate specific gravity in said column to a density approaching that suiiicient to cause its discharge by said current over the rim of the column decreasing the velocity of said currentsufiiciently to cause settling of said intermediate-specificgravity material downwardly in said column, and restoringthe initial velocity of said current before the density of the contents of'said column has been decreased sufliciently by said last-mentioned settling to-permit settling of the coal or other mineral to said lower discharge.

7. A method of separating coal or other minerals of lower specific gravity than" the materials mixed therewith comprising subsuficient velocity to prevent the settling of the heaviest material'downwardly through said column to a discharge at the bottom, and varying the velocity of said current from a maximum to aminimum and back again to the maximum in recurring cycles in such correspondence with increase and decrease of density of the materials accumulated in said column as to cause the'maximum velocity current to stratify material of an intermediate specific gravity in said column and'the coal to overflow the rim'of said column and to cause the minimum velocity current to settle said intermediate-specific-gravity material downwardly before it has accumulated to a density suflicient to overflow the rim of the column and as to cause the restoration of the maximum velocity current before the decrease in density due to the last-mentioned downward settling has become such as to settle the coal downwardly to the bottom discharge. a I v 8. A method of separating coal or other mineral of lower specific gravity than the ma. terials mixed therewith comprising subjecting the mixture with water as a fluid mass in a suitable container to mechamcal and hydraulic agitation permitting settling of the material of heaviest specific gravity downwardly in said container to a bottom discharge but maintaining'the other materials in suspension and floating ofi the mineral over the rim of said container and upon increase in density of said suspended material reducing the hydraulic agitation while continuing the mechanical agitation to prevent discharge over the rim of the container of material other than the coal or other mineral.

9. A method of separating coal or other mineral of lower specific gravity than the materials mixed therewith comprising feeding said mixture to a body of water in a sorting column, mechanically agitating said water and materials to form a fluid mass, causing an upward current of the water in said sorting column to classify the mineral and float ofi v the same over the rim of the column, reducing of an intermediate specific gravit the velocity of said upward current as the density of said fluid mass increases and increasing the velocity of said current as the density of said fluid mass decreases so as to prevent discharge of material other than said mineral over the rim of said column and settling of the mineral with other material to a common discharge below the rim of said column.

10. An apparatus for the classification and separation of materials of different specific gravities comprising, in combination, a water-containing sorting column having a lower and an upper discharge for classified materials, means for feeding a mixture of said materials to said sorting column and for maintaining the mixture with the water as a fluid mass with the materials freely movable in the body of water throughout the sorting column, means for a 'tatin said fluid mass to an extent producing a causing the material of the lowest specific gravity to assume a position in said sorting column in delivery relation to said upper discharge, permitting settling of material of the heaviest specific gravity downwardly to said lower discharge and accumulating material in said sorting'column below said upper ischarge, and automatically operating means for intermittently decreasing and restoring said agitation of the fluid mass to correspondingly decrease and restore the original resistance to downward settling upon increase and decrease in density of said fluid mass in said sorting column and so responsive to changes I in densityas to prevent the accumulation of said intermediate-specific-gravity material in said column to an extent bringing it into delivery relation with said upper discharge and as to prevent the settling of the material of the lowest specific gravity downwardly to said lower discharge.

hindered settling 11. An apparatus as set forth in claim 10' and in which the means for agitating saidfluid mass comprises means for hydraulically agitating said fluid mass.

12. An apparatus for the separation of materials ofi diflercnt specific gravities comprising, in combination, a sorting column having discharges at different levels for classified materials, means for feeding a mixture .of said materials to said column, means for maintaining an upflow stream of water through said column, and automatically operating means for decreasing the velocity of said upflow stream upon an increase in density of stratified materials in the water of said column. 1

13. An apparatus for the separation of materials of difi'erent specific-gravities comprisdischarges at different levels for classified materials, means for feeding a mixture of said .materials to said column, means for maintaining an upflowing stream of water through said sorting column, and automatically operating means for decreasing the velocity of said upflow stream upon an increase in density and for increasing the velocity of said stream upon a decrease in density of Stratified materials in said column.

15. An apparatus for the classification and separation of materials of different specific gravities comprising, in combination, a water-containing sorting column having discharges at different levels for classified materials, means for feeding a mixture of said materials to said column and for maintain-.

ing a continuously upflowing stream of water through said column, and means automatically operating in response to changes in resistance offered by the fluid mass in said sorting column to the passage of the water therethroughto vary the velocity of said upflowing stream. 1

16. The apparatus as set forth in claim 14 and in which the means for maintaining an upflowing stream of water through said sorting column includes a water supply pipe and a valve therein and in which the automatically operating means for decreasing the velocity of said upflow stream upon an increase in density and for increasing the velocity of said stream upon decrease in density of stratified materials in said column comprises a wacrating said valve toward closing position to eflect said decrease in the velocity oit'the upflowstream and toward maximum 0 en position to eflect said increase in the ve ocity of the upflow stream.

17. An apparatus for the classification and separation of materials of difl'erent specific gravities comprising, in combination, a water-containing sorting column having a lower and an upper discharge for classified materials, means for feeding a mixture of said materials to said sorting column and for maintaining the mixture with the water as a fluid mass, means providing a continuously 'upflowing' stream of water in said sorting column of a velocity causing a hindered settling suspending the material of the lowest discharge, I

specific gravity in delivery relation to said upper discharge, permitting settling of materials of the heaviest specificgravity downwardly to said lower discharge and suspending material of an intermediate specific gravity in said sorting column below said upper and automatically operating means for intermittently decreasing and restoring said velocity of water upflow in said sorting column to correspondingly decrease and restore the original resistance to downward settling upon increase and decrease in density of said fluid mass in said sorting column so as to prevent the accumulation of said intermediate-specific-gravity material in said column toan extent bringing it into delivery relation with said upper d1scharge and as to prevent the settling of the lowestspecific-gravity material downwardly to said lower discharge.

18, The apparatus as set forth in claim 17 and in which the means providing an ugflowing stream of water in said sorting co I umn includes a water supply pipe under constant head and a valve therein for controlling the velocity of said stream and in which the automatically operating means for intermittently decreasing and restoring the velocity.

of water upflow comprises a water-expansion chamber so arranged in open communication with said sorting column that as the resistance to upward flow of the water through the fluid mass in the sorting column increases and decreases due to increase and decrease in density arc ne at difl'erent levels for classified materials of diflerent specific gravities, means for feeding a mixture of said materials to said column,

mechanical agitating means and hydraulic agitation means for maintaining said mixture with the water as a fluid mass in said column and for the settling classification of said materials according to their diflering specific gravities, and means responsive to changes in density of said fluid mass as the materials stratify therein and settle out therefrom for decreasing the hydraulic agitationupon an increase in density and increasing the hydraulic agitation upon a decrease in density of said fluid mass.

20. An apparatus for the classification and separation of materials of difl'erent specific gravities com rising, in combination a water sorting cham r having discharges at difl'erent levels for classified materials of different specific gravities, means for, feeding a mixture cludes a perforated plate arranged in said sorting chamber in the path of'the water flow to the mixture in said chamber, said plate being designed to allow materials of said mixture to freely pass therethrough.

In testimony whereof I hereunto aflix my signature. 7

6., NZIES.

of said fluid mass the water respectively rises and falls in said expansion chamber and mechanism actuated by said rise and fall of the water in said expansion chamber for opform distribution through said fluid mass in- 

